Crankcase emission control or PCV valves have previously been used in association with internal combustion engines. These valves usually utilize a valve element movable against the force of a spring to regulate gas and air flow.
A problem with prior valves is relatively large resistance to flow and a tendency for the valve element to oscillate or vibrate particularly at high flow rates. It has been found that prevention of spiral flow through the valve tends to greatly reduce vibration and oscillation.
Still another problem with prior valves is a lack of a shut-off feature when the engine is inoperative. A shut off would isolate the crankcase from external conditions which is desirable.
By way of example, the U.S. Pat. No. 3,662,724 to Ohar discloses a prior crankcase control valve of the same general type as the subject valve. A movable valve element and spring are in the gas flow passage which is undesirable. Likewise, U.S. Pat. No. 3,661,128 displaces the same undesirable feature.